Electronic thermostat

Abstract

Provided are apparatus, including electronic thermostats, for detecting temperatures and elapsed times and, in response to those temperatures and elapsed times, controlling the opening or closing of an electric circuit.

What is claimed is: 
     
       1. An electronic thermostat for use in a mobile heat transfer system, comprising:
 (a) a resistive element with a temperature dependent electrical resistance; and 
 (b) a control circuit comprising a microprocessor;
 wherein said resistive element 
 (i) is configured for monitoring a temperature at an evaporator core of said mobile heat transfer system and 
 (ii) is in electrical contact with said control circuit and is configured for thermal contact with said evaporator core, 
 wherein said microprocessor 
 (i) is programmed to limit a frequency at which a compressor of said mobile heat transfer system cycles, 
 (ii) enables a first-type event that transitions said control circuit from a first state to a second state in response to an electrical resistance of the resistive element corresponding to a predetermined temperature of the evaporator core cut in point and 
 (iii) enables a second-type event that transitions said control circuit from said second state to said first state in response to an electrical resistance of the resistive element corresponding to a predetermined temperature of the evaporator core cut out point 
 wherein a current first-type event does not occur until at least a first predetermined minimum time has elapsed since a prior second-type event and a first preset time delay has elapsed since the response to the electrical resistance corresponding to the predetermined temperature cut in point, 
 wherein a current second-type event does not occur until at least a second predetermined minimum time has elapsed since a prior first-type event and a second preset time delay has elapsed since the response to the electrical resistance corresponding to the predetermined temperature cut out point and 
 wherein said microprocessor is further programmed to enable a second-type event when the control circuit is in the second state and a source voltage connected to the control circuit is less than a predetermined voltage threshold. 
 
 
     
     
       2. The electronic thermostat of  claim 1  wherein said control circuit further comprises a relay that controls an output signal from said control circuit, wherein when said relay is switched on said output signal is on and wherein when said relay is switched off said output signal is off. 
     
     
       3. The electronic thermostat of  claim 2  wherein said microprocessor controls whether said relay is switched on or switched off. 
     
     
       4. The electronic thermostat of  claim 2 , wherein said relay is switched on when said microprocessor detects said predetermined temperature cut in point and wherein said relay is switched off when said microprocessor detects said predetermined temperature cut out point. 
     
     
       5. The electronic thermostat of  claim 1 , wherein said predetermined temperature cut out point is a temperature of between about 27° F. and about 35° F., or between about 28° F. and about 34° F., or between about 29° F. and about 33° F., or between about 30° F. and about 32° F. 
     
     
       6. The electronic thermostat of  claim 1 , wherein said predetermined temperature cut out point is a temperature of about 31° F. 
     
     
       7. The electronic thermostat of  claim 1 , wherein said predetermined temperature cut in point is a temperature of between about 35° F. and about 43° F., or between about 36° F. and about 42° F., or between about 37° F. and about 41° F., or between about 38° F. and about 40° F. 
     
     
       8. The electronic thermostat of  claim 1 , wherein said predetermined temperature cut in point is a temperature of about 39° F. 
     
     
       9. The electronic thermostat of  claim 1 , wherein said electronic thermostat is configured to detect said electrical resistance corresponding to said predetermined temperature cut out and said predetermined temperature cut in within a temperature tolerance of less than ±3° F. 
     
     
       10. The electronic thermostat of  claim 1 , wherein said electronic thermostat is configured to detect said electrical resistance corresponding to said predetermined temperature cut out and said predetermined temperature cut in within a temperature tolerance of about ±1° F. 
     
     
       11. The electronic thermostat of  claim 2 , wherein said microprocessor is programmed such that upon detecting said electrical resistance corresponding to said predetermined temperature cut in point, said microprocessor prevents said current first-type event until at least said first predetermined minimum time has elapsed since said prior second-type event. 
     
     
       12. The electronic thermostat of  claim 1 , wherein said first predetermined minimum time is from about 9 seconds to about 19 seconds, or from about 11 seconds to about 17 seconds, or from about 13 seconds to about 15 seconds. 
     
     
       13. The electronic thermostat of  claim 1 , wherein said first predetermined minimum time is about 14 seconds. 
     
     
       14. The electronic thermostat of  claim 2 , wherein said microprocessor is programmed such that upon detecting said electrical resistance corresponding to said predetermined temperature cut out point, said microprocessor prevents said current second-type event until at least said second predetermined minimum time has elapsed since said prior first-type event. 
     
     
       15. The electronic thermostat of  claim 1 , wherein said second predetermined minimum time is from about 0 seconds to about 2 seconds, or from about 0.5 seconds to about 1.5 seconds. 
     
     
       16. The electronic thermostat of  claim 1 , wherein said source voltage is a DC voltage. 
     
     
       17. The electronic thermostat of  claim 1  wherein said microprocessor is programmed to allow for single step electronic calibration of said resistive element.